(Version 3.2, released January 25, 2022)
Warmest Month Variability
Average Warm Season Variability
Average Warmest Month Variability
Average Within-year Variability
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SST Variability metrics: Historical variability in sea surface temperature (SST) has been related to the level of sensitivity of corals to heat stress, in that higher variability can confer lower sensitivity1. Impacts to less-sensitive corals and reef sites can be lower when they are exposed to particular heat stress levels (as defined by Coral Reef Watch's daily global 5km satellite Coral Bleaching Alert Area product). Historical Variability values are determined at coral reef-containing and adjacent locations worldwide, for 1985-2021, using the Version 3.1 daily global 5km CoralTemp satellite SST data product.
Where relevant, the range of values calculated from analyzed pixels is shown in [brackets] after each metric name.
Warm Season [0.12-1.11°C] and Warmest Month [0.17-1.18°C] Variability: Sites with high summer temperature variability can have less sensitivity to coral bleaching. The Warmest Month is identified in a separate Thermal History product metric (see Climatology page), based on the 28-year (1985-2012) climatology of the CoralTemp SST dataset. The Warm Season is then defined as the three-month period centered on the Warmest Month. For each of these, we determined the average temperature for the stated time period for each year in the time-series (1985-2021); the variability shown is the standard deviation of these values after the removal of any linear trend (see SST Trend page).
Average Warm Season [0.27-1.62°C] and Average Warmest Month [0.19-1.01°C] Variability: For these two metrics, the standard deviation of temperature for the stated time period (Warm Season or Warmest Month) is determined for each year in the time-series (1985-2021) and averaged over the entire time series.
Annual Variability [0.11-0.95°C]: This metric speaks to the variability between years, which can modify the impact of heat stress events and the susceptibility of corals and reef sites to future events2. This aids in identifying coral reef locations for which the thermal regime is dominated by high inter-annual variability, when compared with the climatological range (e.g., in the central Pacific, linked to phases of the El Niño-Southern Oscillation cycle; see the Climatology page). For the Annual Variability metric, we determined the average temperature for each year in the time-series (1985-2021); the variability shown is the standard deviation of these values after the removal of any linear trend (see SST Trend page).
Average Within-year (Intra-annual) Variability [0.37-6.04°C]: For this metric, the standard deviation of temperature is determined for each year in the time-series (1985-2021) and averaged over the entire time series.
1Guest JR, et al. (2012) Contrasting Patterns of Coral Bleaching Susceptibility in
2010 Suggest an Adaptive Response to Thermal Stress. PLoS ONE 7(3): e33353.
2Donner SD (2011) An evaluation of the effect of recent temperature variability on the prediction of coral bleaching events. Ecological Applications 21(5): 1718-1730.